JP2005268510A - Manufacturing method of soi substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of industrially manufacturing a sound partial SOI structure including non-stepped portion between the SOI region and non-SOI region with the SIMOX method. <P>SOLUTION: The manufacturing method of SOI substrate comprises steps of: forming a protection film to form a mask for ion implantation on the surface of a semiconductor substrate formed of silicon single crystal; forming an aperture to the protection film to form the mask having the predetermined pattern; implanting the oxygen ion from the surface of the semiconductor substrate; and forming an embedded oxide film within the semiconductor substrate with heat treatment of the semiconductor substrate. This method is characterized in that the heat treatment process to form the embedded oxide film is conducted in at least twice or more times and the heat treatment is conducted at least once or more without removal of the protection film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an SOI substrate in which an SOI (Silicon-On-Insulator) structure element and a bulk structure element, which are manufactured by a SIMOX (Separation by IMplanted Oxygen) technique, are combined.

  Conventionally, as a method for manufacturing this kind of SOI substrate, as shown in FIG. 2, a protective film 2 is formed on the surface of the semiconductor substrate 1 (FIG. 2A), and the protective film 2 is formed by lithography. Oxygen ions 4 are implanted from the surface of the substrate 3 (FIG. 2B) (FIG. 2C), a predetermined cleaning process is performed, and a high-temperature heat treatment is performed to form the buried oxide film 5 (see FIG. 2 (D) and (E)), a method for manufacturing an SOI and bulk-embedded semiconductor substrate is disclosed (Non-patent Document 1, Patent Document 1, and Patent Document 2). In these SOI substrate manufacturing methods, a semiconductor substrate on which a thin film SOI structure and a bulk structure are mixed can be manufactured. The structural elements can be arranged on the same substrate.

However, these conventional methods for manufacturing an SOI substrate have a problem that a step is generated between the SOI region and the non-SOI region (bulk structure region) (see FIG. 3). The allowable step depends on the circuit pattern size of the target integrated circuit, but is currently said to be about 200 nm or less, and it is known that the allowable step value becomes smaller. Among the conventionally disclosed methods for manufacturing SOI substrates, the cleaning process before heat treatment is performed when the protective film is removed (Non-Patent Document 1) and when it is not removed (Patent Document 1 and Patent Document 2). However, in any case, in the conventional method for manufacturing an SOI substrate, it is difficult to realize an allowable step, and the integration progresses and the size of the circuit pattern becomes small. Further, as the allowable step becomes smaller, it is extremely difficult to make the step less than the allowable value in the conventional method for manufacturing an SOI substrate.
JP 2001-308025 A See Japanese Patent Laid-Open No. 2001-308172, FIG. H. L. Ho et al. , IEDM Tech. Dig. Cat. No. 01CH37224, 2001: 22.3.1-4

  Accordingly, an object of the present invention is to provide a method for manufacturing an SOI substrate having such a step that is reduced and an allowable step is provided.

  The above objects are achieved by the following (1) to (2).

  (1) forming a protective film for forming a mask against ion implantation on the surface of a semiconductor substrate made of silicon single crystal, forming an opening in the protective film, and forming a mask with a predetermined pattern; A method for manufacturing an SOI substrate, comprising: implanting oxygen ions from the surface of the semiconductor substrate; and heat-treating the semiconductor substrate to form a buried oxide film inside the semiconductor substrate, wherein the buried oxide film A method for manufacturing an SOI substrate, wherein the heat treatment step for forming the substrate is performed at least twice, and the heat treatment is performed at least once without removing the protective film.

  (2) The method for manufacturing an SOI substrate according to claim 1, wherein the heat treatment step includes a heat treatment step of a heat treatment temperature of 1250 ° C. or higher, an oxygen flow rate ratio during heat treatment of 20% or higher, and a processing time of 30 minutes or longer.

  In the method for manufacturing an SOI substrate described in (1) above, since the heat treatment process for forming the buried oxide film is divided into two or more times, the heat treatment is performed without removing the protective film, and the protective film is removed. Both the heat treatment and the heat treatment can be performed. Therefore, a step generated between the SOI region and the non-SOI region (bulk structure region) can be reduced.

  Further, in the method for manufacturing an SOI substrate described in the above (2), it is possible to further reduce a step generated between the SOI region and the non-SOI region (bulk structure region) (see Table 1).

  As described above, the present invention is a method for manufacturing an SOI substrate according to the above-described method, wherein a step generated between an SOI region and a non-SOI region (bulk structure region) is reduced. A manufacturing method is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

  Here, FIG. 1 is a flowchart showing an example of a manufacturing process of an SOI substrate according to the present invention. Hereinafter, a case where the protective film is a thermal oxide film will be described.

  In FIG. 1, an oxide film, which is a protective film 12 for forming a mask against ion implantation, is formed on the surface of a semiconductor substrate 11 made of silicon single crystal by thermal oxidation (FIG. 1A). An opening 13 is formed in the protective film 12 in order to form a mask having a predetermined pattern by lithography (FIG. 1B). Oxygen ions 14 are implanted from the surface of the semiconductor substrate 11 (FIG. 1C), and the semiconductor substrate 11 is heat-treated to form a buried oxide film 15 in the semiconductor substrate 11 (FIG. 1D). (E)). At this time, as the heat treatment step, first, heat treatment is performed without removing the protective film 12 (FIG. 1D), and then the protective film 12 and the thermal oxide film 16 formed by the heat treatment are washed with diluted hydrofluoric acid. Then, heat treatment is performed (FIG. 1E). After the heat treatment, the thermal oxide film 17 is removed (FIG. 1F).

  At this time, it is preferable that the opening 13 is formed by anisotropic etching, and the mask is formed so that the edge is close to a perpendicular angle with respect to the substrate.

  The protective film may be any film that shields oxygen ions. In the case of silicon, a thermal oxide film, a CVD oxide film, a CVD nitride film, or the like can be used.

In the case of an SOI substrate by the SIMOX method, oxygen ions are implanted at an acceleration energy of, for example, 180 keV and a dose of, for example, 4 × 10 ¹⁷ atoms / cm ² to form a high-concentration oxygen ion-implanted layer at a predetermined depth. The heat treatment temperature is set at, for example, 1350 ° C., and the heat treatment is performed in an atmospheric gas in which, for example, 0.5% concentration of oxygen is added to argon, for example, for 4 hours, and then the oxygen concentration is set at, for example, 70%. Manufactured in a process such as performing a time heat treatment. In this case, in the present invention, for example, first, the heat treatment temperature is set to 1350 ° C., and the substrate is taken out of the heat treatment furnace after being heat-treated in an atmosphere gas in which 0.5% concentration of oxygen is added to argon. This is immersed in dilute hydrofluoric acid to remove the thermal oxide film, which is a protective film, and the thermal oxide film formed by heat treatment. Subsequently, the heat treatment temperature is set to 1350 ° C., and oxygen at 70% concentration is added to argon. Heat treatment for 4 hours. However, the manufacturing condition of the SIMOX substrate is not particularly limited to this.

  In order to control the thickness of the Si layer on the buried oxide film in the SOI region, thermal oxidation in a dry atmosphere or a wet atmosphere is further performed at 800 to 1250 ° C., and a potassium hydroxide aqueous solution or ammonia is peroxidized. It is also possible to perform etching with a mixed aqueous solution of hydrogen or the like.

  Hereinafter, the present invention will be specifically described with reference to Examples.

Examples 1-5 and Comparative Examples 1-2
Boron-doped single crystal silicon was grown by the Czochralski method, and a wafer with a diameter of 200 mm was prepared with the (001) plane serving as the main surface of the substrate. A 1 μm thick thermal oxide film was formed on this wafer, an opening was formed by reactive ion etching so that the silicon surface was exposed, and a mask for ion implantation was formed. Next, oxygen ion implantation was performed at a substrate temperature of 550 ° C., an acceleration voltage of 180 keV, and an implantation dose of 4 × 10 ¹⁷ cm ⁻² . These wafers were put into a heat treatment furnace, and heat treatment and protective film removal were performed according to the procedures and conditions shown in Table 1. At the same time, the SOI substrate was manufactured using the conventional technology.

  After the surface oxide layer was removed from the manufactured SOI substrate with hydrofluoric acid, a step at the SOI / bulk boundary was observed using an AFM (atomic force microscope). The observation results are summarized in Table 1.

The flowchart which shows the characteristics of the manufacturing process of the SOI substrate by this invention. The flowchart which shows the characteristics of the manufacturing process of the SOI substrate by a prior art. The schematic diagram which shows the level | step difference between SOI / bulk area | regions produced by a prior art.

Explanation of symbols

1,11 ... Semiconductor substrate,
2,12 ... Protective film,
3, 13 ... opening,
4, 14 ... oxygen ions,
5, 15 ... buried oxide film,
6, 16, 17 ... thermal oxide film,
7 ... steps.

Claims (2)

  Forming a protective film for forming a mask against ion implantation on a surface of a semiconductor substrate made of silicon single crystal; forming an opening in the protective film to form a mask with a predetermined pattern; and the semiconductor substrate A method for manufacturing an SOI substrate, comprising: implanting oxygen ions from the surface of the substrate; and heat-treating the semiconductor substrate to form a buried oxide film inside the semiconductor substrate, wherein the buried oxide film is formed. A method for manufacturing an SOI substrate, wherein the heat treatment step is performed at least twice, and the heat treatment is performed at least once without removing the protective film.   2. The method for manufacturing an SOI substrate according to claim 1, wherein the heat treatment step includes a heat treatment step in which a heat treatment temperature is 1250 ° C. or more, an oxygen flow rate ratio during heat treatment is 20% or more, and a treatment time is 30 minutes or more.

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